Nowadays, people pay much attention to the air quality in the environment. For example, it is important to monitor carbon monoxide, carbon dioxide, volatile organic compounds (VOC), Particulate Matter 2.5 (PM2.5), nitric oxide, sulfur monoxide, and so on. The exposure of these substances in the environment will cause human health problems or even harm the life. Therefore, it is important for every country to monitor the air quality in the environment, which is a topic currently being valued.
Generally, it is feasible to use a gas sensor to monitor the air quality in the environment. If the gas sensor is capable of immediately providing people with the monitored information relating to the environment for caution, it may help people escape or prevent from the injuries and influence on human health caused by the exposure of the substances described above in the environment. In other words, the gas sensor is suitably used for monitoring the ambient air in the environment.
Currently, to achieve reaction detection, the gas is transported to the reaction material of a surface of the gas sensor, and thus gas monitoring is performed. Moreover, as shown in FIG. 1, the gas sensor 2 is usually disposed in a separated detecting chamber 1 for performing gas detection, and thus the detected gas would not be interfered by external factors. The detecting chamber 1 has an inlet 1a and an outlet 1b. The external gas enters the detecting chamber 1 through the inlet 1a by natural convection and flows slowly, after which the gas is spread to the surface of the gas sensor 2 for performing the reaction detecting, and discharged through the outlet 1b, so that the gas detection is achieved. Since the gas to be monitored by the gas sensor 2 is guided into the detecting chamber 1 by natural convection, it takes too long to transport the gas so that the sensing efficiency of the gas sensor 2 is negatively affected, and the immediate detection cannot be achieved.
In order to solve the above-mentioned problem and achieve the immediate detection, a fan (not shown) is assembled in the detecting chamber 1. Generally, a conventional fan is rotary motor-driven type. Although the fan speeds up the gas transportation to the detecting chamber 1, the sensitivity of sensing by the gas sensor 2 may be affected and distorted as the flow rate of the gas increases or chaos airflow occurs. This is because the gas molecule cannot be caught by the gas sensor 2 immediately for being dissolved in or bonded to the reaction material on the surface of the gas sensor 2. In addition, it takes time for the reaction material to react with the caught gas molecule. Therefore, a stable airflow of the gas flowing over the surface of the gas sensor 2 is required. The way of increasing the flow rate of gas by the fan is not suitable because it would cause high flow rate or chaos airflow. Moreover, as the fan is utilized to increase the flow rate of gas, a period of acceleration time is required for driving the fan while the fan is activated, so that the fan is driven to rotate at a specific rotational speed and generate high flow rate of gas. In addition, a period of deceleration time is required for stopping the fan from rotating. Therefore, when the fan is activated or deactivated, a period of acceleration time or deceleration time is required as the fan is driven in an inertial way. Since activating and deactivating the fan both take a period of time, adopting the fan to increase the flow rate of gas is not suitable for immediate detection. Consequently, there is a need of making the gas transportation appropriate for achieving the immediate detection.
There is a need to improve the gas sensor in monitoring the gas with accurate sensitivity and immediate response. In addition, there is a need of miniaturizing the gas sensor and the detecting chamber for possessing portability and monitoring everywhere and any time. If the fan is utilized to increase the flow rate of gas, the volume of the fan is hard to be miniaturized. Consequently, the present disclosure provides a portable gas detecting device capable of monitoring and sampling immediately.